Enterotoxigenic E. coli (ETEC) are effective pathogens only if they can both colonize the small bowel of a susceptible species and produce toxin(s). The fimbrial adhesins that permit colonization of the small intestine by ETEC are highly species specific and ETEC that are human pathogens do not cause natural secretory diarrheal disease in animals. We previously identified a number of naturally occurring E. coli isolates associated with the small intestines of BALB/c mice. These isolates were shown to express chromosomally encoded, mannose resistant hemagglutination (MRHA) of human type A erythrocytes. To identify this MRHA factor, a cosmid genomic library of one of these isolates was constructed and a number of clones that express MRHA activity equivalent to that expressed by the wild type strain were identified. This MRHA operon was characterized by restriction mapping and was subcloned as a 20 kb insert in plasmid pBR325. Transpositional mutagenesis using $\lambda$::TnphoA-1 yielded a number of MRHA negative isolates containing the junction fragment between one MRHA open reading frame (orfA) and bacterial alkaline phosphatase (phoA) from TnphoA indicating that the coding product of orfA plays a critical role in the synthesis and assembly of the MRHA. A 2.2 kb plasmid (pJB71) containing an intact orfA coding sequence was subsequently identified and its nucleotide sequence was determined. A computerized sequence analysis of this plasmid indicated that the 2.2 kb insert is part of the MRHA operon which shares significant homology with E. coli papABCDEFGHIJK, prsA and prsH genes. All these genes are associated with P pili which mediate digalactoside-specific binding to human uroepithelial cells in ascending, unobstructive renal infections / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_23491 |
| Date | January 1994 |
| Contributors | Bao, Jianxiong (Author), Clements, John D (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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